Abstract
Globally, lake surface water temperatures have warmed rapidly relative to air temperatures, but changes in deepwater temperatures and vertical thermal structure are still largely unknown. We have compiled the most comprehensive data set to date of long-term (1970–2009) summertime vertical temperature profiles in lakes across the world to examine trends and drivers of whole-lake vertical thermal structure. We found significant increases in surface water temperatures across lakes at an average rate of + 0.37 °C decade−1, comparable to changes reported previously for other lakes, and similarly consistent trends of increasing water column stability (+ 0.08 kg m−3 decade−1). In contrast, however, deepwater temperature trends showed little change on average (+ 0.06 °C decade−1), but had high variability across lakes, with trends in individual lakes ranging from − 0.68 °C decade−1 to + 0.65 °C decade−1. The variability in deepwater temperature trends was not explained by trends in either surface water temperatures or thermal stability within lakes, and only 8.4% was explained by lake thermal region or local lake characteristics in a random forest analysis. These findings suggest that external drivers beyond our tested lake characteristics are important in explaining long-term trends in thermal structure, such as local to regional climate patterns or additional external anthropogenic influences.
Original language | English |
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Article number | 20514 |
Journal | Scientific Reports |
Volume | 10 |
Issue number | 1 |
DOIs | |
State | Published - Dec 2020 |
Externally published | Yes |
Funding
This work was conceived at the Global Lake Ecological Observatory Network (GLEON), and benefited from continued participation and travel support from GLEON. This manuscript is dedicated to the late Alon Rimmer and Karl Havens, who provided data and contributed to earlier versions of this manuscript. Funding in support of this work came from the following sources: Belarus Republican Foundation for Fundamental Research; IGB Long-Term Research; the European Commission within the MANTEL project; the DFG within the LimnoScenES project (AD 91/22-1); OLA-IS, AnaEE-France, INRAE of Thonon-les-Bains, CIPEL, SILA, CISALB; Universidad del Valle de Guatemala; Archbold Biological Station; the Oklahoma Department of Wildlife Conservation, the Oklahoma Water Resources Board, the Grand River Dam Authority, the US Army Corps of Engineers, and the City of Tulsa; the Ministry of Business, Innovation, and Employment (UOW X1503); the Natural Environment Research Council of the UK; the IGB’s International Postdoctoral Fellowship; NSERC, Canada Foundation for Innovation, Canada Research Chairs, Province of Saskatchewan; University of Regina; Queen’s University Belfast; Natural Environment Research Council; US-NSF, California Air Resources Board, NASA, and US National Park Service; the Ministry of Higher Education and Research (projects № FZZE-2020-0026; № FZZE-2020-0023) and RSCF 20-64-46003; US National Science Foundation Long Term Research in Environmental Biology program (DEB-1242626); the Environmental Agency of Verona; US National Science Foundation, the Gordon and Betty Moore Foundation, the Mellon Foundation, and the University of Washington; KMFRI, LVEMP, University of Innsbruck, OeAD, IFS, and LVFO-EU; Waikato Regional Council and Bay of Plenty Regional Council; Swedish Environmental Protection Agency and the Swedish Infrastructure for Ecosystem Sciences; US National Science Foundation grants DEB-1754276 and DEB-1950170. We thank J. Klug, P. McIntyre, H. Swain, K. Tominaga, A. Voutilainen, and L. Winslow for their feedback on early drafts that substantially improved this manuscript. Additional detailed acknowledgements can be found in the Supplementary Information online.